The present invention relates to transmitting circuits, receiving circuits, and communication systems equipped therewith and more particularly to a transmitting circuit and a receiving circuit that transmit signals via transformers, and a communication system equipped with these circuits.
In recent years, a communication means that utilizes magnetic coupling of a transformer has become widely used as a short-range communication means. In the communication means that utilizes magnetic coupling, however, a transformer includes coils, and each coil has an inductor. Here, waveforms of pulses used for transmitting and receiving are distorted owing to self-resonances caused by the inductors. As a result, in a communication means that utilizes magnetic coupling, it is necessary that the reciprocal of a pulse transmission duration (referred to as a data rate hereinafter) is limited up to about a third of the self-resonant frequencies of the inductors.
On the other hand, there is a need for the increase of communication speed even in the short-range communication. Therefore, technologies that increase the communication speed in the communication systems that utilize magnetic coupling are disclosed in Non-patent documents 1 to 5. A technology in which a communication speed is improved by installing plural transformers and parallelizing outgoing and incoming signals is disclosed in Non-patent document 1.
[Non-patent document 1]
    N. Miura, D. Mizoguchi, M. Inoue, K. Niitsu, Y. Nakagawa, M. Tago, M. Fukaishi, T. Sakurai, and T. Kuroda, “A 1 Tb/s 3 W inductive-coupling transceiver for 3D-stacked inter-chip clock and data link”, IEEE Journal of Solid-State Circuits, vol. 42, 2007, pp. 111-122[Non-patent document 2]    N. Miura, D. Mizoguchi, M. Inoue, T. Sakurai, and T. Kuroda, “A 195-Gb/s 1.2-W inductive inter-chip wireless superconnect with transmit power control scheme for 3-D-stacked system in a package”, IEEE Journal of Solid-State Circuits, vol. 41, 2006, p. 23[Non-patent document 3]    N. Miura, D. Mizoguchi, T. Sakurai, and T. Kuroda, “Analysis and design of inductive coupling and transceiver circuit for inductive inter-chip wireless superconnect”, IEEE Journal of Solid-State Circuits, vol. 40, 2005, p. 829[Non-patent document 4]    S. Kawai, H. Ishikuro, and T. Kuroda, “A 2.5 Gb/s/ch 4PAM inductive-coupling transceiver for non-contact memory card”, 2010 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC), 2010, pp. 264-265[Non-patent document 5]    N. Miura, Y. Kohama, Y. Sugimori, H. Ishikuro, T. Sakurai, and T. Kuroda, “A high-speed inductive-coupling link with burst transmission”, IEEE Journal of Solid-State Circuits, vol. 44, no. 3, pp. 947-955, 2009.